Abstract 4955: PD-L1 expression on circulating epithelial tumor cells (CETCs) correlates with the presence of metastasis in breast cancer patients and differs from PD-L2 expression

1001 Background: Metastasis is the main cause of cancer-related death. Single disseminated tumor cells (DTC) can be detected by sensitive immunocytochemical and molecular technologies, but it is still unclear whether these cells are viable and biologically active. Methods: We applied a novel enzyme-linked immunospot assay (‘EPISPOT‘) that reveals a fingerprint of specific proteins secreted from single viable epithelial tumor cells. The membrane of ELISPOT plates were coated with monoclonal antibodies against the tumor-associated marker proteins mucin-1 (MUC1) for breast cancer and prostate-specific antigen (PSA) for prostate cancer. In addition, dual fluorescent EPISPOT assays were developed to characterize MUC1+ and PSA+ cells (i.e. CK19, FGF2 secretion). Results: Even in the absence of overt metastases (stage M0), the EPISPOT assay revealed viable tumor cells in the peripheral blood of 65% of prostate cancer patients (n=31) and the bone marrow of 54% of breast cancer patients (n=37). Respective samples from non-carcinoma controls were EPISPOT- negative, whereas 80 to 100% of samples from metastatic patients (stage M1, n=40) were positive. The number of EPISPOT-positive cells in M0-patients ranged from 2 to 197 in the blood of prostate cancer patients and 1 to 262 in the bone marrow of breast cancer patients, while M1- patients showed significantly higher counts (prostate cancer, 1–684; breast cancer, 4–813). Interestingly, subsets of MUC1- or PSA-secreting cells expressed a breast stem cell-like phenotype (MUC1-/CK19+) or secreted FGF-2 as factor relevant for the growth of DTC, respectively. Conclusions: A significant fraction of cancer patients harbor viable and biologically active tumor cells in their blood and bone marrow, even in the absence of overt metastases. The multiparameter EPISPOT assay helps to identify these putative metastatic precursor cells. No significant financial relationships to disclose.

Download Full-text

Prospective Monitoring of Circulating Epithelial Tumor Cells (CETC) Reveals Changes in Gene Expression during Adjuvant Radiotherapy of Breast Cancer Patients

Current Oncology ◽

10.3390/curroncol28050302 ◽

2021 ◽

Vol 28 (5) ◽

pp. 3507-3524

Author(s):

Matthias Mäurer ◽

Katharina Pachmann ◽

Thomas Wendt ◽

Dorothea Schott ◽

Andrea Wittig

Keyword(s):

Breast Cancer ◽

Single Cell ◽

Tumor Cells ◽

Early Stage ◽

Breast Cancer Patients ◽

Ki 67 ◽

Epithelial Tumor ◽

Before And After ◽

Epithelial Tumor Cells ◽

Cell Expression

Circulating epithelial tumor cells (CETC) are considered to be responsible for the formation of metastases. Therefore, their importance as prognostic and/or predictive markers in breast cancer is being intensively investigated. Here, the reliability of single cell expression analyses in isolated and collected CETC from whole blood samples of patients with early-stage breast cancer before and after radiotherapy (RT) using the maintrac® method was investigated. Single-cell expression analyses were performed with qRT-PCR on a panel of selected genes: GAPDH, EpCAM, NANOG, Bcl-2, TLR 4, COX-2, PIK3CA, Her-2/neu, Vimentin, c-Met, Ki-67. In all patients, viable CETC were detected prior to and at the end of radiotherapy. In 7 of the 9 (77.8%) subjects examined, the CETC number at the end of the radiotherapy series was higher than before. The majority of genes analyzed showed increased expression after completion of radiotherapy compared to baseline. Procedures and methods used in this pilot study proved to be feasible. The method is suitable for further investigation of the underlying molecular biological mechanisms occurring in cells surviving radiotherapy and possibly the development of radiation resistance.

Download Full-text